/*
 * tf/idf implementation 
 * Author: Thanh Dao, thanh.dao@gmx.net
 */
using System;
using System.Collections;


namespace ServiceRanking
{
	/// <summary>
	/// Summary description for TF_IDFLib.
	/// </summary>
	public class TFIDFMeasure
	{
		private string[] _docs;
        //private string[][] _ngramDoc;
		private int _numDocs=0;
		private int _numTerms=0;
		private ArrayList _terms;
		private int[][] _termFreq;//
		private float[][] _termWeight;//
		private int[] _maxTermFreq;
		private int[] _docFreq;

        public delegate void OnProgressChangeEventHandler(float total,float count);
        public OnProgressChangeEventHandler OnProgressChangeEvent;
        public delegate void OnProgressStartEventHandler(string mes);
        public delegate void OnProgressEndEventHandler();
        public OnProgressStartEventHandler OnProgressStartEvent;
        public OnProgressEndEventHandler OnProgressEndEvent;

        void OnProgressing(float total, float count) {
            if (OnProgressChangeEvent != null)
                OnProgressChangeEvent(total, count);
        }

        void OnProgressStart(string mes) {
            if (OnProgressStartEvent != null)
                OnProgressStartEvent(mes);
        }

        void OnProgresseEnd() {
            if (OnProgressEndEvent != null)
                OnProgressEndEvent();
        }

		public class TermVector
		{		
			public static float ComputeCosineSimilarity(float[] vector1, float[] vector2)
			{
				if (vector1.Length != vector2.Length)				
					throw new Exception("DIFER LENGTH");
				

				float denom=(VectorLength(vector1) * VectorLength(vector2));
				if (denom == 0F)				
					return 0F;				
				else				
					return (InnerProduct(vector1, vector2) / denom);
				
			}

			public static float InnerProduct(float[] vector1, float[] vector2)
			{
			
				if (vector1.Length != vector2.Length)
					throw new Exception("DIFFER LENGTH ARE NOT ALLOWED");
				
			
				float result=0F;
				for (int i=0; i < vector1.Length; i++)				
					result += vector1[i] * vector2[i];
				
				return result;
			}
		
			public static float VectorLength(float[] vector)
			{			
				float sum=0.0F;
				for (int i=0; i < vector.Length; i++)				
					sum=sum + (vector[i] * vector[i]);
						
				return (float)Math.Sqrt(sum);
			}

		}

		private IDictionary _wordsIndex=new Hashtable() ;

		public TFIDFMeasure()
		{}

        public void LoadDocs(string[] documents) {
            _docs = documents;
            _numDocs = documents.Length;
            MyInit();
        }

		private ArrayList GenerateTerms(string[] docs)
		{
            OnProgressStart("GenerateTerms");
			ArrayList uniques=new ArrayList() ;
			for (int i=0; i < docs.Length ; i++)
			{
				Tokeniser tokenizer=new Tokeniser() ;
				string[] words=tokenizer.Partition(docs[i]);			

				for (int j=0; j < words.Length ; j++)
					if (!uniques.Contains(words[j]) )				
						uniques.Add(words[j]) ;
                OnProgressing(docs.Length,i+1);
			}
            OnProgresseEnd();
			return uniques;
		}

		private static object AddElement(IDictionary collection, object key, object newValue)
		{
			object element=collection[key];
			collection[key]=newValue;
			return element;
		}

		private int GetTermIndex(string term)
		{
			object index=_wordsIndex[term];
			if (index == null) return -1;
			return (int) index;
		}

		private void MyInit()
		{
			_terms=GenerateTerms (_docs );
			_numTerms=_terms.Count ;

			_maxTermFreq=new int[_numDocs] ;
			_docFreq=new int[_numTerms] ;
			_termFreq =new int[_numTerms][] ;
			_termWeight=new float[_numTerms][] ;
            OnProgressStart("initialize terms");
			for(int i=0; i < _terms.Count ; i++)			
			{
				_termWeight[i]=new float[_numDocs] ;
				_termFreq[i]=new int[_numDocs] ;
				AddElement(_wordsIndex, _terms[i], i);
                OnProgressing(_terms.Count,i);
			}
            OnProgresseEnd();
			GenerateTermFrequency ();
			GenerateTermWeight();			
				
		}
		
		private float Log(float num)
		{
			return (float) Math.Log(num) ;//log2
		}

		private void GenerateTermFrequency()
		{
            OnProgressStart("GenerateTermFrequency");
			for(int i=0; i < _numDocs  ; i++)
			{								
				string curDoc=_docs[i];
				IDictionary freq=GetWordFrequency(curDoc);
				IDictionaryEnumerator enums=freq.GetEnumerator() ;
				_maxTermFreq[i]=int.MinValue ;
				while (enums.MoveNext())
				{
					string word=(string)enums.Key;
					int wordFreq=(int)enums.Value ;
					int termIndex=GetTermIndex(word);

					_termFreq [termIndex][i]=wordFreq;
					_docFreq[termIndex] ++;

					if (wordFreq > _maxTermFreq[i]) _maxTermFreq[i]=wordFreq;					
				}
                OnProgressing(_numDocs,i);
			}
            OnProgresseEnd();
		}
		

		private void GenerateTermWeight()
		{
            OnProgressStart("GenerateTermWeight");
			for(int i=0; i < _numTerms   ; i++)
			{
				for(int j=0; j < _numDocs ; j++)				
					_termWeight[i][j]=ComputeTermWeight (i, j);
                OnProgressing(_numTerms, i);
			}
            OnProgresseEnd();
		}

		private float GetTermFrequency(int term, int doc)
		{			
			int freq=_termFreq [term][doc];
			int maxfreq=_maxTermFreq[doc];			
			
			return ( (float) freq/(float)maxfreq );
		}

		private float GetInverseDocumentFrequency(int term)
		{
			int df=_docFreq[term];
			return Log((float) (_numDocs) / (float) df );
		}

		private float ComputeTermWeight(int term, int doc)
		{
			float tf=GetTermFrequency (term, doc);
			float idf=GetInverseDocumentFrequency(term);
			return tf * idf;
		}
		
		public  float[] GetTermVector(int doc)
		{
			float[] w=new float[_numTerms] ;
			for (int i=0; i < _numTerms; i++)											
				w[i]=_termWeight[i][doc];
			
				
			return w;
		}

		public float GetSimilarity(int doc_i, int doc_j)
		{
			float[] vector1=GetTermVector (doc_i);
			float[] vector2=GetTermVector (doc_j);

			return TermVector.ComputeCosineSimilarity(vector1, vector2) ;

		}
		
		private IDictionary GetWordFrequency(string input)
		{
			string convertedInput=input.ToLower() ;
					
			Tokeniser tokenizer=new Tokeniser() ;
			String[] words=tokenizer.Partition(convertedInput);			
			Array.Sort(words);
			
			String[] distinctWords=GetDistinctWords(words);
						
			IDictionary result=new Hashtable();
			for (int i=0; i < distinctWords.Length; i++)
			{
				object tmp;
				tmp=CountWords(distinctWords[i], words);
				result[distinctWords[i]]=tmp;
				
			}
			
			return result;
		}				
				
		private string[] GetDistinctWords(String[] input)
		{				
			if (input == null)			
				return new string[0];			
			else
			{
				ArrayList list=new ArrayList() ;
				
				for (int i=0; i < input.Length; i++)
					if (!list.Contains(input[i])) // N-GRAM SIMILARITY?				
						list.Add(input[i]);
				
				return Tokeniser.ArrayListToArray(list) ;
			}
		}

		private int CountWords(string word, string[] words)
		{
			int itemIdx=Array.BinarySearch(words, word);
			
			if (itemIdx > 0)			
				while (itemIdx > 0 && words[itemIdx].Equals(word))				
					itemIdx--;				
						
			int count=0;
			while (itemIdx < words.Length && itemIdx >= 0)
			{
				if (words[itemIdx].Equals(word)) count++;				
				
				itemIdx++;
				if (itemIdx < words.Length)				
					if (!words[itemIdx].Equals(word)) break;					
				
			}
			
			return count;
		}				
	}
}
